1. Field
The disclosed technology relates generally to implantable medical devices, and more particularly, to implantable medical devices including an implantable electrode assembly.
2. Related Art
A variety of implantable medical devices have been proposed to deliver controlled electrical stimulation to a region of a subject's body to achieve a therapeutic effect. Such devices, generally referred to herein as stimulating medical devices, include muscle or tissue stimulators, brain stimulators (deep brain stimulators, cortical stimulators, etc.), cardiac pacemakers/defibrillators, functional electrical stimulators (FES), spinal cord stimulators (SCS), pain stimulators, stimulating hearing prostheses, etc. Such stimulating medical devices include one or more electrode contacts that deliver electrical stimulation signals to the subject (commonly referred to as a patient, recipient, etc.; “recipient” herein). In addition, the stimulating medical devices may also include one or more electrode contacts to monitor and/or measure a particular biological activity, sometimes broadly referred to as sensors.
Hearing loss, which may be due to many different causes, is generally of two types, conductive and sensorineural. In some cases, a person suffers from hearing loss of both types. Conductive hearing loss occurs when the normal mechanical pathways for sound to reach the cochlea, and thus the sensory hair cells therein, are impeded, for example, by damage to the ossicles. Individuals who suffer from conductive hearing loss typically have some form of residual hearing because the hair cells in the cochlea are undamaged. As a result, individuals suffering from conductive hearing loss typically receive an acoustic hearing aid that generates mechanical motion of the cochlea fluid.
In many people who are profoundly deaf, however, the reason for their deafness is sensorineural hearing loss. Sensorineural hearing loss occurs when there is damage to the inner ear, or to the nerve pathways from the inner ear to the brain. As such, those suffering from some forms of sensorineural hearing loss are thus unable to derive suitable benefit from hearing prostheses that generate mechanical motion of the cochlea fluid. As a result, medical devices having one or more implantable components that deliver electrical stimulation signals to a patient or recipient have been developed. Certain such implantable medical devices include an array of stimulating electrode contacts that deliver the stimulation signals to nerve cells of the recipient's auditory system, thereby providing the recipient with a hearing percept.
As used herein, the recipient's auditory system includes all sensory system components used to perceive a sound signal, such as hearing sensation receptors, neural pathways, including the auditory nerve and spiral ganglion, and parts of the brain used to sense sounds. Electrically-stimulating implantable medical devices include, for example, auditory brain stimulators and cochlear prostheses (commonly referred to as cochlear prosthetic devices, cochlear implants, cochlear devices, and the like; simply “cochlear implants” herein).
Oftentimes sensorineural hearing loss is due to the absence or destruction of the cochlear hair cells that transduce acoustic signals into nerve impulses. It is for this purpose that cochlear implants have been developed. Cochlear implants provide a recipient with a hearing percept by delivering electrical stimulation signals directly to the auditory nerve cells, thereby bypassing absent or defective hair cells that normally transduce acoustic vibrations into neural activity. Such devices generally use an electrode array implanted in the cochlea so that the electrodes may differentially activate auditory neurons that normally encode differential pitches of sound.